n,*a=$<.read.split.map &:to_i
f=->u{
	[*0...a.size].combination(3).find{|i,j,k|
		(a[i]-a[j])*(a[j]-a[k])<0&&(v=1<<i|1<<j|1<<k;(u&v)==0&&!f[u|v])
	}
}
puts (f[0]||[-1])*' '